.\" Copyright (c) 1995
.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
.\"
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.Dd April 12, 1995
.Dt ETHERS 5
.Os
.Sh NAME
.Nm ethers
.Nd ethernet address database
.Sh DESCRIPTION
The
.Nm
database contains information regarding known 48-bit ethernet addresses
of hosts on an Internetwork.
The data is stored in a file called
.Pa /etc/ethers
in the following format:
.Pp
.D1 Ar ethernet-address fully-qualified-host-name
.Pp
Items are separated by any number of blanks and/or
tab characters.
A ``#'' at the start of a line indicates the
beginning of a comment that extends to the end of the line.
A ``+'' at
the start of a line will cause the
.Xr ethers 3
library functions to use data stored in the
.Tn NIS
.Pa ethers.byname
and
.Pa ethers.byaddr
maps in addition to the data in the
.Pa /etc/ethers
file.
.Pp
An ethernet address is expressed in
.Tn ASCII
form as "x:x:x:x:x:x" where
.Ar x
is a hexadecimal value between 0x00 and 0xFF.
The address values
should be in network order.
Hostnames specified in the
.Pa /etc/ethers
database should correspond to entries in the
.Xr hosts 5
file.
.Pp
The
.Fn ether_line
function in the standard C library can be used to break individual
lines in the
.Pa /etc/ethers
database into their individual components: a binary Ethernet address
stored as an
.Pa ether_addr
structure, and a hostname stored as a character string.
.Sh FILES
.Bl -tag -width /etc/services -compact
.It Pa /etc/ethers
The
.Nm
file resides in
.Pa /etc .
.El
.Sh SEE ALSO
.Xr ethers 3 ,
.Xr yp 8
.Sh HISTORY
The
.Nm
format is based on the format used in SunOS 4.1.x.
